An experimental method for accurately determining residual gas content of coal samples
By combining degassing and acid hydrolysis methods, and utilizing the reaction of sulfuric acid solution with coal to release methane gas, the problem of measurement error in residual methane content of coal samples with pores smaller than 0.38 nm in existing technologies has been solved, and accurate determination of methane content has been achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- DATONG COAL MINING GROUP XUANGANG COAL & ELECTRICITY CO LTD JIAOJIAZHAI COAL MINE
- Filing Date
- 2025-10-29
- Publication Date
- 2026-05-29
AI Technical Summary
Existing technologies are insufficient to accurately determine the residual gas content in coal samples with pores smaller than 0.38 nm, leading to errors in experimental results.
A combination of degassing and acid hydrolysis was used. The Fenton reaction between sulfuric acid solution and coal disrupted the non-covalent bonds between molecules. Methane gas was released by shaking on a shaker, and the methane concentration was determined by gas chromatography. The total residual methane content was calculated by combining the measurement results from the degassing and acid hydrolysis methods.
It achieves complete release and accurate measurement of methane gas in coal samples with pores smaller than 0.38 nm, solving the measurement error problem in existing technologies and improving measurement accuracy.
Smart Images
Figure CN122109352A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of residual gas content determination technology in coal samples, specifically to an experimental method for accurately determining the residual gas content in coal samples. Background Technology
[0002] Residual gas content is generally defined as the amount of gas remaining in a coal block or coal body after a period of gas release under standard atmospheric pressure; that is, the amount of non-desorbable gas at normal pressure. Residual gas content serves as an important basis for calculating the coalbed methane resource reserves in mines, predicting mine gas outbursts, and preventing the risk of mine gas outbursts. Therefore, accurate measurement of residual gas content is of great significance for preventing gas outburst risks and for the exploitation of coalbed methane resources in my country.
[0003] Existing laboratories typically use the degassing method to determine the residual gas content. This method relies on the principle that residual gas in the coal sample seeps outward under negative pressure due to the gas pressure gradient. The residual gas content is determined by the direct proportionality between the seepage rate and the coal sample temperature and the degree of coal fragmentation.
[0004] However, this degassing method is only effective for coal samples with pore sizes of 1.50 nm or larger. When the pore size is less than 0.38 nm, relying solely on the principle of residual gas seeping outward under negative pressure is insufficient to remove all residual gas. Furthermore, the residual gas content is susceptible to errors in the experimental results due to the difficulty in measuring the degree of coal sample breakage. Therefore, it is necessary to provide a more accurate experimental method for determining the residual gas content in coal samples to address these technical problems. Summary of the Invention
[0005] The purpose of this invention is to provide an experimental method for accurately determining the residual gas content in coal samples, thereby solving the problem of difficulty in accurately detecting the residual gas content in coal samples in the prior art.
[0006] To achieve the above objectives, the present invention provides the following technical solution: an experimental method for accurately determining the residual gas content in coal samples, comprising the following steps: S1. The residual gas content of the coal sample to be tested was determined by the degassing method.
[0007] S2. The residual gas content of the coal sample was further determined by acid hydrolysis.
[0008] The total residual gas content is calculated based on the measurement results of S3, the combined degassing method, and the acid hydrolysis method.
[0009] The specific process of step S1 is as follows: S101. Fresh coal samples collected from the coal seam in the mining area are placed into a vacuum container, and after ensuring good sealing, they are brought to the laboratory for further processing. S102. The coal sample in the vacuum container is heated to 95°C and then degassed under vacuum. The gas extracted from the container is then analyzed by gas chromatography. S103. Grind the coal sample to be tested into powder using a sealed ball mill. For fresh coal samples, the powdering degree should reach more than 90%, and the particle size of the coal sample should be less than 0.25 mm.
[0010] S104. The ball mill jar containing the crushed coal sample is heated to 95°C according to the coal sample degassing step in step S102 to degas the coal sample until there is no more gas desorption in the overall coal sample, and the gas extracted from the container is analyzed by gas chromatography.
[0011] The specific process of step S2 is as follows: S201. To test the airtightness of the reagent bottle, place the coal sample that has been tested by the degassing method into a sealed reagent bottle, add sulfuric acid solution, stir and mix, and then seal and store. The sealed reagent bottle should consist of three parts: a 500ml reagent bottle, a hollow round cap, and a rubber stopper. After evenly applying Vaseline to the bottle opening, seal it with the hollow round cap containing the rubber stopper and immerse it in clean water for 5 minutes to check for leaks. The added sulfuric acid solution should have a concentration of 0.05mol / L and a pH of 1. Furthermore, the amount of sulfuric acid solution used should be 100ml for every 50g of coal sample, and the total volume should not exceed one-third of the reagent bottle's capacity.
[0012] S202. Evacuate the reagent bottle to a vacuum state, and then repeat the headspace replacement nitrogen operation three times. When using a vacuum pump to evacuate the reagent bottle, the negative pressure inside the bottle is maintained between 0 and 0.1 kPa. A puncture needle with a three-way valve is used to draw pure nitrogen headspace to replace the gas inside the bottle, so that the gas pressure inside the bottle is stabilized near the standard atmospheric pressure.
[0013] S203. Place the reagent bottle on a shaker and vibrate for 6 hours to analyze the reagent. S204. Use a gas chromatograph to determine the concentration of gas released into the reagent bottle; S205. Repeat steps S202 to S204 until the concentration of the gas precipitated in the reagent bottle no longer changes. S206. Weigh the residual coal after washing and drying following the experiment.
[0014] The specific process of step S3 is as follows: S301. Calculate the residual gas content of the coal sample to be tested as determined by the degassing method.
[0015] The calculation formula is: In the formula: —The residual gas content in the coal sample determined by the degassing method, in cm³. 3 / g; —Gas concentration determined by degassing method, % V – Volume of degassed gas determined by the degassing method, in cm³ 3 ; —Ash content of coal sample, % —Moisture content of the coal sample, % m — Mass of coal sample, in grams; S302. Calculate the residual gas content in coal samples determined by acid hydrolysis method; The calculation formula is: In the formula: —Residual gas content in coal samples determined by acid hydrolysis, in cm³ 3 / g; —Gas concentration determined by acid hydrolysis method, % V – Headspace volume, in cm³ 3 ; —Ash content of coal sample, % —Moisture content of the coal sample, % m — Mass of coal sample, in grams; S303. According to the above degassing method and acid hydrolysis method process, the gas release process is repeated multiple times until the gas concentration no longer changes. The total amount of gas released each time can be used to obtain the total residual gas content. The calculation formula is: W – Total residual gas content in the coal sample, in cm³. 3 / g; —The residual gas content of the coal sample determined for the first time by the degassing method, in cm³. 3 / g; —The residual gas content of the coal sample determined by the second degassing method, in cm³. 3 / g; —The residual gas content of the coal sample determined for the first time by acid hydrolysis, in cm³. 3 / g; —The residual gas content of the coal sample determined by the second acid hydrolysis method, in cm³. 3 / g; —The residual gas content in a coal sample determined by acid hydrolysis when the gas concentration no longer changes, in cm³. 3 / g.
[0016] Compared with the prior art, the beneficial effects of the present invention are: This invention relates to an experimental method for accurately determining the residual gas content in coal samples. Based on the degassing method for determining the residual gas content in coal samples, this method utilizes the principle that sulfuric acid solution can react with coal via the Fenton reaction. This reaction oxidizes and breaks down the large molecular structure of coal into smaller molecules and destroys the non-covalent bonds between molecules. This allows the residual gas inside the coal sample with pores smaller than 0.38 nm to be completely released under shaking. The concentration of the released gas is then determined using a gas chromatograph, enabling precise calculation of the residual gas content in the coal sample. This method solves the problem of existing experimental methods being unable to accurately determine the residual gas concentration in coal samples. Attached Figure Description
[0017] Figure 1 This is a schematic flowchart of an experimental method for accurately determining the residual gas content in coal samples according to the present invention. Figure 2 The graph shows the residual gas concentration curves after 6 hours of acidolysis of coal samples with sulfuric acid solutions of different concentrations. Detailed Implementation
[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0019] Please see Figure 1-2 This invention provides a technical solution: an experimental method for accurately determining the residual gas content in coal samples, comprising the following steps: S1. The residual gas content of the coal sample to be tested was determined by the degassing method.
[0020] S101. When collecting coal samples for testing, fresh coal samples should be collected from the coal seams in the mining area. After collection, the coal samples should be immediately placed in a vacuum container, ensuring a good seal, and then brought to the laboratory for storage and later use. S102. Take the coal sample out of the vacuum container and place it in a heating container. Heat the coal sample in the container to 95°C using a heating instrument and then perform vacuum degassing. Perform gas chromatography analysis on the gas extracted from the container. S103. Grind the coal sample to be tested into powder using a sealed ball mill jar; When crushing fresh coal samples for testing, it is necessary to ensure that the particle size of the coal sample with a crushing degree of more than 90% is less than 0.25mm.
[0021] S104. The ball mill jar containing the crushed coal sample is heated to 95°C according to the coal sample degassing step in step S102 to degas the coal sample until there is no more gas desorption in the overall coal sample, and the gas extracted from the container is analyzed by gas chromatography.
[0022] S2. The residual gas content of the coal sample was further determined by acid hydrolysis.
[0023] S201. To test the airtightness of the reagent bottle, place the coal sample that has been tested by the degassing method into a sealed reagent bottle, add sulfuric acid solution, stir and mix, and then seal and store. The sealed reagent bottle should include the following three parts: a 500ml reagent bottle, a hollow round cap, and a rubber stopper; after evenly applying Vaseline to the mouth of the reagent bottle, seal it with the hollow round cap containing the rubber stopper, and press it into clean water for five minutes to observe whether there is any leakage; when adding sulfuric acid solution, 100ml of sulfuric acid solution with a concentration of 0.05mol / L and a pH value of 1 should be added for every 50g of coal sample, and the total volume should not exceed one-third of the reagent bottle.
[0024] S202. Evacuate the reagent bottle to a vacuum state, and then repeat the headspace replacement nitrogen operation three times. When using a vacuum pump to evacuate the reagent bottle, the negative pressure inside the bottle is maintained between 0 and 0.1 kPa. A puncture needle with a three-way valve is used to draw pure nitrogen headspace to replace the gas inside the reagent bottle, so that the gas pressure inside the bottle is stabilized near the standard atmospheric pressure. S203. Place the reagent bottle on a shaker and vibrate for 6 hours to analyze the reagent. S204. Use a gas chromatograph to determine the concentration of gas released into the reagent bottle; S205. Repeat steps S202 to S204 until the concentration of the gas precipitated in the reagent bottle no longer changes. S206. Weigh the residual coal after washing and drying following the experiment.
[0025] The total residual gas content is calculated based on the measurement results of S3, the combined degassing method, and the acid hydrolysis method.
[0026] S301. Calculate the residual gas content of the coal sample to be tested as determined by the degassing method.
[0027] The calculation formula is: In the formula: —The residual gas content in the coal sample determined by the degassing method, in cm³. 3 / g; —Gas concentration determined by degassing method, % V – Volume of degassed gas determined by the degassing method, in cm³ 3 ; —Ash content of coal sample, % —Moisture content of the coal sample, % m — Mass of coal sample, in grams; S302. Calculate the residual gas content in coal samples determined by acid hydrolysis method; The calculation formula is: In the formula: —Residual gas content in coal samples determined by acid hydrolysis, in cm³ 3 / g; —Gas concentration determined by acid hydrolysis method, % V – Headspace volume, in cm³ 3 ; —Ash content of coal sample, % —Moisture content of the coal sample, % m — Mass of coal sample, in grams; S303. According to the above degassing method and acid hydrolysis method, the gas release process is repeated multiple times until the gas concentration no longer changes. The total residual gas content can be obtained by accumulating the amount of gas released each time.
[0028] The calculation formula is: W – Total residual gas content in the coal sample, in cm³. 3 / g; —The residual gas content of the coal sample determined for the first time by the degassing method, in cm³. 3 / g; —The residual gas content of the coal sample determined by the second degassing method, in cm³. 3 / g; —The residual gas content of the coal sample determined for the first time by acid hydrolysis, in cm³. 3 / g; —The residual gas content of the coal sample determined by the second acid hydrolysis method, in cm³. 3 / g; —The residual gas content in a coal sample determined by acid hydrolysis when the gas concentration no longer changes, in cm³. 3 / g.
[0029] It should be noted that in this article, relational terms such as first and second are only used to refer to... Distinguishing one entity or operation from another does not necessarily require or imply any such actual relationship or order between those entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.
[0030] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.
Claims
1. A method for accurately determining the residual gas content in coal samples, characterized in that, Includes the following steps: S1. The residual gas content of the coal sample to be tested is determined by the degassing method; S2. Further determine the residual gas content of the coal sample using acid hydrolysis method; S201. Place the coal sample with residual gas content determined by the degassing method in a sealed reagent bottle, add sulfuric acid solution, stir and mix, and then seal and store. S202. Perform headspace replacement with nitrogen after evacuating the reagent bottle; S203. Place the reagent bottle on a shaker and continue to vibrate and analyze for 6 hours; S204. Use a gas chromatograph to determine the concentration of the gas released from the reagent bottle; S205. Repeat steps S202 to S204 until the concentration of the gas precipitated in the reagent bottle no longer changes. S206. Weigh the residual coal after washing and drying following the experiment. S3. Calculate the total residual gas content based on the measurement results of the degassing method and the acid hydrolysis method; S301. Calculate the residual gas content of the coal sample to be tested as determined by the degassing method; The calculation formula is: In the formula: —The residual gas content in the coal sample determined by the degassing method, in cm³. 3 / g; —Gas concentration determined by degassing method, % V – Volume of degassed gas determined by the degassing method, in cm³ 3 ; —Ash content of coal sample, % —Moisture content of the coal sample, % m — Mass of coal sample, in grams; S302. Calculate the residual gas content in coal samples determined by acid hydrolysis method; The calculation formula is: In the formula: —Residual gas content in coal samples determined by acid hydrolysis, in cm³ 3 / g; —Gas concentration determined by acid hydrolysis method, % V – Headspace volume, in cm³ 3 ; —Ash content of coal sample, % —Moisture content of the coal sample, % m — Mass of coal sample, in grams; S303. According to the above degassing method and acid hydrolysis method process, the gas release process is repeated multiple times until the gas concentration no longer changes. The total amount of gas released each time can be used to obtain the total residual gas content. The calculation formula is: W – Total residual gas content in the coal sample, in cm³. 3 / g; —The residual gas content of the coal sample determined for the first time by the degassing method, in cm³. 3 / g; —The residual gas content of the coal sample determined by the second degassing method, in cm³. 3 / g; —The residual gas content of the coal sample determined for the first time by acid hydrolysis, in cm³. 3 / g; —The residual gas content of the coal sample determined by the second acid hydrolysis method, in cm³. 3 / g; —The residual gas content in a coal sample determined by acid hydrolysis when the gas concentration no longer changes, in cm³. 3 / g.
2. The experimental method for accurately determining the residual gas content in coal samples according to claim 1, characterized in that, Step S1 includes: S101. Freshly collected coal samples are placed in a vacuum container and stored in the laboratory for later use. S102. The coal sample is placed in a container and heated to 95°C, then degassed under vacuum, and the gas extracted from the container is analyzed by gas chromatography. S103. Grind and crush the coal sample to be tested in a closed structure; S104. The coal sample, after being crushed in a closed structure, is heated to 95°C according to the coal sample degassing step in step S102 to degas the coal sample until there is no more gas desorption in the overall coal sample, and the extracted gas is analyzed by gas chromatography.
3. The experimental method for accurately determining the residual gas content in coal samples according to claim 2, characterized in that: In step S103, the fresh coal sample to be tested should be pulverized to a degree of over 90%, with the particle size of the coal sample being less than 0.25 mm.
4. The experimental method for accurately determining the residual gas content in coal samples according to claim 1, characterized in that: The sealed reagent bottle in step S201 includes a 500ml reagent bottle, a hollow round cap, and a rubber stopper.
5. The experimental method for accurately determining the residual gas content in coal samples according to claim 4, characterized in that: In step S201, the sealing performance of the reagent bottle is tested before placing the coal sample in the reagent bottle. That is, after evenly applying Vaseline to the mouth of the reagent bottle, it is sealed with a hollow round cap containing a rubber stopper and pressed into clean water for 5 minutes to observe whether there is any air leakage.
6. The experimental method for accurately determining the residual gas content in coal samples according to claim 1, characterized in that: In step S201, 100 ml of sulfuric acid solution should be added to every 50 g of coal sample, and the total volume should not exceed one-third of the reagent bottle.
7. The experimental method for accurately determining the residual gas content in coal samples according to claim 6, characterized in that: In step S201, the sulfuric acid solution has a concentration of 0.05 mol / L and a pH value of 1.
8. The experimental method for accurately determining the residual gas content in coal samples according to claim 1, characterized in that: In step S202, when the vacuum pump is used to evacuate the reagent bottle, the negative pressure inside the reagent bottle is maintained between 0 and 0.1 kPa.
9. The experimental method for accurately determining the residual gas content in coal samples according to claim 1, characterized in that: In step S202, when headspace purging nitrogen, a puncture needle with a three-way valve is used to draw pure nitrogen for headspace purging of the gas inside the reagent bottle, so that the gas pressure inside the bottle is stabilized near the standard atmospheric pressure.
10. The experimental method for accurately determining the residual gas content in coal samples according to claim 9, characterized in that: The headspace nitrogen replacement operation in step S202 is repeated three times.